pleural (adj.)

"sereus membrane lining the chest cavity," early 15c., from medical Latin, from Greek pleuron "a rib," in plural, pleura, "the ribs, side of the body," also "flank of an army, page of a book," a word of unknown origin.

suffix forming adjectives from nouns or other adjectives, "of, like, related to, pertaining to," Middle English -al, -el, from French or directly from Latin -alis (see -al (2)).